Method of mitigating corrosion in wells



ting a casing in the borehole, inserting a string of been flushed with water, placing a packer in the annulus between the casing and tubing to close V temperatures are lower.

i trained by the hydrocarbon stream, and during UNITED sTATEs PATENT OFFICE METHOD F MITIGATING CORROSION IN WELLS William F. Oxford, Jr., Beaumont, Tex.,-as,signor l to Sun Oil Company, Philadelphia,v Pa., a corporation of New Jersey Y Application December 5, 1945, Serial No. 632,862

1 3 Claims. (Cl. 252-8.55) This invention relates to petroleum production and particularly has to do with the prevention or mitigation of corrosion in oil and gas Wells.

'Ihe completion of a well for the production of petroleum hydrocarbons generally comprises set- 5 and iron. These materials in the presence of water and under elevated temperatures as encountered in wells may undergo hydrolysis to form the corresponding'inorganic acids which are capable of attacking well tubing. In other cases hydrogen sulfide dissolved in water carried by the hydrocarbon stream may be effective to promote corrosion of metal parts.

'Ihe present invention is directed to overcoming corrosion problems of the above indicated type and provides a method of preventing or mitigating such corrosion. According to the invention, an ion exchange material adapted to react with the corrosive constituent is introduced into the well and brought into cpntact with the hydrocarbon flow streamto remove the corrosive constituent therefrom by ion exchange reaction before it has had the opportunity to attack the well tubing appreciably. Either` ananion exchange material or a cation exchanger, or both, may be employed dependent upon what the particular constituent is that is apt to cause the corrosion. For example, in gas-distillate wells where the relatively low boiling organic acids are the cause, an anion exchange material capable of replacing theaeid/ anion by an hydroxyl ion may be usedrf'nion exchangers suitable for this purpose'are well known and include resins such as amine-formaldehyde, basic dyestuff such as aniline black, natural inorganic adsorbents such as hydroxyapatite and dolomite 'and synthetic heavy-metal silicates. Such exchangers may also be employed where aqueousA hydrogen sul. de or phenol is the cause of corrosion.

tubing within the casing and, after the well has on' the upper part of the casing so as not to subl0 ject it to the pressure of the productive zone. The casing often is placed through the productive zone and the bottom of the casing is sealed off by means of cement. the well then being opened up for production by gun perforation of the casing adjacent the oil stratum. The 'well is then permitted to produce through the tubing.

It has been foundv that in certain cases the well tubing is subjected to corrosion due to corrosive constituents that are carried in the` hydrocarbon flow stream. While this is not so often the case in wells producing crude oil, it has been found to be particularly true in high pressure gasdistillate` wells wherein the main part oi the hydrocarbon ow is in the vapor phase. The hydrocarbon vapors carry along appreciable. amounts of water which in the lower portion ofthe well may be entirely in vapor form due tothe higher prevailing temperatures or 'the water mayV f be present as finely divided liquid particles especlallyl ign/,the upper part of the well where the Corrosion in gas-distillate wells has been noted to occur especially severely in the upper portion of the wells (as also inthe well fittings and ilow lines), perhaps being coextensive with the zone wherein the temperature is sufllciently low that water can be present in liquid state.

It has now been found Vthat the corrosion in gas-distillate wells is due largely to the presence of small but appreciable amounts of low boiling organic acids, such as formic acid, acetic acid. propionlc acid, etc.. whichare carried along by the hydrocarbon ilow. These acids are present in the water which condenses froml or is ension results from the presence of hydrolyzable inorganic salts of magnesium. calcium or iron in the water carried by the iiow stream, a cation exchangerv may be'used which is capable of removing the magnesium, calcium or iron cation and replacing it by an alkali metal ion such as sodium. Known exchangers ofthis type are the zeolites which include processed green sand and synthetic gel zeolite. Alternatively, the hydrolyzable salts may, if desired, be removed by contacting the flow stream rst with a cation exchanger capable of substituting the hydrogen ion for the metallic cation and immediately lthereafter with an anion exchanger to remove the resulting inorganic acid. Cation exchangers suitable as the rst Contact material include resins such as tannin-formaldehyde and phenol-formaldehyde, certain phenolic sulfonic acid derivatives and sulfonated carbonaceous materials such as coal, lignite and peat.

the course of prolonged operation of the well are capable of causing extremely severecorrosion of the well tubing, ttings and flow lines. Other acidic constituents which are encountered in some gas producing wells and which likewise may be corrosive are phenolic compounds.

In some cases corrosion of well tubing may re, sult from the presence of inorganic salts such as the sulfates or chloridesof magnesium, calcium On the other hand, in cases Where thecorrof`Y The accompanying drawing, which illustrates a mode of carrying out the invention, is a diagrammatic vertical sectional view of the lower portion of an oil well.

In the drawing, I vrepresents a lower portion of the well casing which extends down through A the productive formation II into the formation tubing I4 extending below the packer I 5 has.

perforations to permit the ow of fluids from the productive formation into the tubing and the end of the tubing is closed as shown at I 6'. A container I1 made of perforated sheet metal or plastic material or of heavy wire screen is positioned within the well tubing Il and contains an ion exchange material adapted to remove the corrosive constituent from the flow stream. The upper portion of container I1 is designed so that the container may be lowered into or withdrawn from the tubing on a conventional wire line and is provided with a locking device I 9 which may be of any known or suitable type for securing the container in place within the tubing.

With the arrangement as shown, the hydrocarbon stream flows from the productive zone II 1 through casing perforations I3 and into the tubing through perforations 20. thence into thecontainer I1 wherein the ilow stream comes in intimate contact with the ion exchange material or adsorbent I8, whereby the corrosive constituent is removed by ion exchange reaction. Afterfthe adsorbent has been used for suillcient time to become saturated and lose its effectiveness for further removal of the corrosive constituent, it may be regenerated in situ by shutting off the well flow; injecting into the tubing a regenerating solution and permitting the solution to contact the adsorbent. Where the adsorbent is an anion exchanger, a solution of suitable alkali, such as sodium carbonate or caustic soda, may be used as the regenerating agent. In the case of cation exchangers regeneration maybe effected by an acid solution. Also, if desired, the container I1 may be periodicallyremoved from the well and the used adsorbent replaced by freshmaterial.

It will be understood that the above described embodini'ent is merely illustrative ofone means of practicing the invention and that many modications maybe made within the scope of the invention. For example, in dually completed wells wherein `the well is permitted to produce from one horizon through the tubing while also producing from another horizon through the annular space between tubing and casing, corrosion within the tubing may be mitigated in the manner abovedescribed while corrosion of the outer surface cf the tubingv and inner surface of the casing may be prevented by suitably positioningl a batch of the ion exchange adsorbent in the annular space to contact the hydrocarbon now therein. Again, in cases where corrosion is apt to occur only in the upper part of the well, it may be desirable to place the adsorbent at an upper level in the well rather than near the bottom of the tubing. For example, in high pressure gas-distillate wells it has been observed that most of the corrosion occurs at depths above 3000 feet; evidently because it is only .within this shallower zone that the temperature is suiliciently low that water carried by the hydrocarbon vapors can condense and form an aqueous organic acid phase. In such cases it may be desirable to place the ion exchange adsorbent near the lower edge of this zone where condensation first occurs.

`What I claim and desire to protect by Letters Patent is:

1. In the production of petroleum hydrocarbons through a 'well .wherein the hydrocarbon flow stream contains a constituent tending to cause corrosion of the well tubing, the method of mitigating such corrosion which 'comprises placingf within the well a granular mass of ion exchange material adapted to remove the corrosive constituent from the hydrocarbon stream by ion exchange reaction, and bringing the hydrocarbon stream in contact with the ion exchange material to remove said constituent. Y

2. In the production of petroleum hydrocarbons through a gas-distillate well wherein the hydrocarbon flow stream contains low boiling organic acids which tend to cause corrosion of the well tubing, the method of mitigating such corrosion which comprises placing withinthe well a granular mass of anion Iexchange materiall adapted to react y.by ion exchange with such organic acids, bringing the hydrocarbon stream in contact with the ion exchange material and thereby removing said organic acids.

3. In the production of petroleum hydrocarbons through a well wherein the hydrocarbon flow stream contains an inorganic salt capable of hydrolyzing to form an inorganic acid corrosive to the well tubing, the method of mitigating such corrosion which comprises placing within the well a granular mass of. cation exchange material adapted to exchange an alkali metal ion for the cation of said salt, and bringing the hydrocarbon stream in contact with the ion exchange material to eiect the ion exchange.

' WILLIAM F. OXFORD, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,829,705 Walker I Oct. 27, 1931 1,873,084 Walker II Aug. 23, 1932 2,226,134 lLiebknecht et al. Dec. 24, 1940 2,357,559 Smith Sept, 5, 1944- 2,360,195 Brittin Oct, 10, 1944 2,366,008 DAlelio Dec. 26, 1944 2,388,235 Bowman et al Nov. 6, 1945 

